The present invention relates to a gas-lance apparatus and method for injecting a rate-enhancing gas between a flame and a thermal load to augment combustion of the fuel undergoing combustion in the flame. More particularly, the present invention relates to such a gas-lance apparatus and method in which fan-shaped main and booster jets of the rate-enhancing gas are introduced between the flame and the thermal load to deform the flame into the shape of the main jet and to draw the flame in the direction of the thermal load.
Many industrial processes involve burning a fuel to heat a thermal load such as a melt composed of, for instance, metals, ferric and non-ferric, glass, and etc. In order to increase the heat transfer to the thermal load, it is also known to inject a rate-enhancing gas, such as oxygen or oxygen-enriched air into the fuel. Burners that employ a rate-enhancing gas in the combustion of a fuel are known in the art as oxy-fuel burners.
The problem with oxy-fuel burners is that the heat transfer tends to be relatively concentrated, and as a result, hot spots tend to develop in the melt. In order to prevent this, gas-lancing method and apparatus have been provided in the prior art. A prior art gas-lancing method and apparatus is illustrated in U.S. Pat. No. 4,927,357. In such gas-lancing method and apparatus, rate-enhancing gas is injected between a burner or a fuel nozzle and a melt by way of an oxidant nozzle which imparts a fan-shaped configuration to the rate-enhancing gas jet. This fan-shaped rate-enhancing gas jet produces a low pressure field which tends to attract the flame towards the melt while deforming the flame toward the shape of the fan-shaped rate-enhancing gas jet. This produces burning over a wide area with more homogeneous heat transfer which avoids any hot spots developing in the melt.
A problem with prior art gas-lancing is that the jet of rate-enhancing gas tends to decay over its length due to entrainment of combustion-environment gas. As a result, the degree to which the flame eminating from the fuel jet or burner can be influenced is somewhat limited.